#!/bin/bash
# Usage: "Linux - CPU usage monitor.sh 75 95"
# 
# Description:
#   This script is used from inside of Tactical RMM instances to check the CPU usage. 
#   This script should be deployed as a check script.
#
# Options:
#   Arg1 - Warning limit
#   Arg2 - Error limit
#
# Author: D. de Kooker (info@dcomputers.nl)
# Sources: https://www.activexperts.com/support/network-monitor/online/linux/
# Changelog :
#   27-06-2022 - Initial script from source, tweaked for my environment
#   16-09-2023 - Changed the way the CPU performance is monitored to TOP, because of false positives in alerting.

# Default values for WARNING and ERROR limits
WARNING_LIMIT=85
ERROR_LIMIT=95

# Check for command line arguments
if [ $# -eq 2 ]; then
  WARNING_LIMIT=$1
  ERROR_LIMIT=$2
fi

# Function to check CPU usage
check_cpu_usage() {
  CPU_USAGE=$(top -bn1 | grep 'Cpu(s)' | awk '{print int($2)}')
  if [ "$CPU_USAGE" -ge "$ERROR_LIMIT" ]; then
    echo "ERROR: CPU usage is $CPU_USAGE% (>= $ERROR_LIMIT%)"
    exit 1
  elif [ "$CPU_USAGE" -ge "$WARNING_LIMIT" ]; then
    echo "WARNING: CPU usage is $CPU_USAGE% (>= $WARNING_LIMIT%)"
    exit 2
  else
    echo "OK: CPU usage is $CPU_USAGE%"
    exit 0
  fi
}

check_cpu_usage